According to World Health Organization (WHO) criteria, anemia is defined as blood hemoglobin (Hb) concentration < 130 g/L (< 13 g/dL) or hematocrit (Hct) < 39% in adult males; Hb < 120 g/L (< 12 g/dL) or Hct < 37% in adult females. Here, GSTM1 is linked to anemia (phenotype).